Microwave antenna



v FM? ME w Dec. 6, 1960 G. A. WALTERS MICROWAVE ANTENNA Filed Oct. 18, 1954 FIEJL 2 Sheets-Sheet 1 INVENTOR.

GLENN ,4; MLTERS rrow/5w vi RL UNE Dec. 6, 1960 e. A. WALTERS MICROWAVEANTENNA Filed Oct. 18, 1954 2 Sheets-Sheet 2 FIIEl 7 'FIE E INVENTOR.GLENN 14. M ALTERS United States Patent C) MICROWAVE ANTENNA Glenn A.Walters, Atherton, Calif., assignor to The Dalmo Victor Company, SanCarlos, Calif., a corporation of California Filed Oct. 18, 1954, Ser.No. 462,927

18 Claims. (Cl. 343-709) This invention relates to a microwave antennaand more specifically to a radar antenna for use on a submarine.

The principal object of this invention is to provide a microwave antennahaving a broadband means for rotating the plane of polarization of apropagated wave.

Another object of this invention is to provide a micro- Wave antennahaving a plurality of radiating sources wherein said sources are soarranged to reduce the etfects of scattered radiation resulting fromsaid plurality of radiating sources.

A further object of this invention is to provide a microwave radarantenna having a parabolic feed to an array of sectoral horns.

A further object of this invention is to provide a microwave radarantenna having a parabolic feed to an array of sectoral horns whereinthere is provided a broadband impedance match to both air and water,whereby the antenna may be submerged without damage to the transmitter.

A still further object of this invention is to provide a submarine radarantenna which is streamlined in its exterior configuration, whereby thedrag of the antenna when submerged is reduced to a minimum.

Various other objects of the invention will be apparent from reading thefollowing description taken in conjunction with the accompanyingdrawings, in which:

Fig. 1 is a perspective view of an antenna embodying the principles ofmy invention, certain parts being broken away to reveal details of otherelements located therebehind.

Fig. 2 is a transverse section taken on line 2-2 of Fig. 1.

Fig. 3 is a partial section taken on line 3-3 of Fig. 1, showing a frontview of a portion of the sectoral horn array.

Fig. 4 is a partial plan view of the elements shown in Fig. 3.

Fig. 5 is a sectional view taken on line 5-5 of Fig. 1, showing thedetails of the hinge construction and the spring for biasing the hingedhousing section toward its open position.

Fig. 6 is a side elevation of one of the dielectric windows removed fromthe horn in which it is mounted.

Fig. 7 is a plan view of the window shown in Fig. 6.

Referring now to the drawings, there is disclosed an antenna comprisinga housing, generally indicated by the reference numeral 10, havingformed in its lower end portion a double-layer pillbox comprising alower layer 13 and an upper layer 14 separated by a metal partition 35.The housing is supported by a vertical post 12 extending generallyunderneath the mid-portion of the housing 10.

An input waveguide 11 terminates in an energy radiating window 15located in the lower layer of the pillbox structure. The waveguide isconnected to a source of transverse electromagnetic waves and said wavesare radiated from the window 15 to be focused by a parabolic reflector16 adjacent the forward end of the pillbox structure, the parabolicreflector being so constructed that its focus is at the window 15. Thewaves having been focused by the parabolic reflector travel back alongthe upper layer 14 of the pillbox and travel around a developed bend 17,and enter a plurality of step-twisted sections generally indicated at18. These step-twisted sections are best seen in the perspective viewshown in Fig. l and they function to receive the vertically polarizedwave emanating from the parabolic reflector and rotate the polarizationof the wave to the horizontal position in three steps labeledrespectively 19, 20 and 21. Each of these step-twisted sections forrotating the polarization of the emanating wave is connected to one of abattery of twenty-two sectoral horns, indicated by the reference numeral22, and arranged in side by side relation with the center to centerdistance between horns being equal to or greater than one-halfwavelength.

Certain of the horns 22 are spaced rearwardly of the remainder of thehorns by a distance equal to an odd multiple of one-quarter wavelengthsof the wave being emanated in order to provide a better impedance matchand reduce the reflections in the radiating system. The spacing of thesehorns is not accomplished in a regular pattern. However, the pattern issymmetrical about the center of the antenna. Considering the horns asnumbered consecutively from one end of the array to the other, horns 3,4, 5, 9, 11, 13, 15, 16, 17, 21 and 22 are spaced one-quarter wavelengthor an odd multiple of one-quarter wavelengths behind the remainder ofthe horns, since it has been found by experimentation that thisparticular arrangement ofthe horns is the best arrangement forsuppressing deleterious side eflects of the wave emanating from one hornupon the wave issuing from the horns adjacent thereto since by thisarrangement it is possible to break up the pattern of the scatteredradiation emanating from the individual horns so that reinforcement ofindividual radiated components is avoided. In this manner, the overallside lobe energy is held below a desired minimum in any given direction.

In order to prevent water from entering the horns and into the antennasystem, and also to provide a broadband impedance match to either wateror air, each of the horns 22 has a dielectric window 23 sealed into itsopen or flared end. The dielectric windows are best illustrated in Figs.6 and 7 and each comprises a main section 24 which is the same width asthat of the horn at its flared end. A generally square inwardlyprojecting portion 25 formed with a taper 26 on its side edges conformsto the internal dimensions of the flared horn 22 and is sealinglyengaged therewith. A vertically extending rectangular section 27 extendsfrom the forward face of the block 24. A square block 28 projectsinwardly from the section 25, and similarly, a square block 29 projectsforward from the rectangular section 27. The upper surface 30 of each ofthese windows is tapered downwardly and outwardly away from the horn atan angle of approximately 25. A Window designed in this manner willprovide a broadband impedance to match the antenna output to either airor water and thereby eliminate the possibility of damage to thetransmitter should the antenna be inadvertently submerged while thetransmitter is still energerized.

A non-reflecting lossy dielectric 31 is provided in the rear portionofthe antenna housing to absorb any back radiation which may emanatefrom the waveguide feed.

The forward half of the upper surface of the housing is in the form of aflap 32 which is hinged to the remainder of the housing by means of apiano type hinge 33. A torsion spring 34 surrounds the pin of the pianotype hinge and bears against the undersurface of the flap and thestationary portion of the housing in order to bias the flap toward itsoutwardly extended position illustrated in the dot-dash lines in Fig. 2.When in this outwardly extended position, the flap 32 forms one side ofa large flared horn to help in the vertical shaping of the beamemanating from the antenna. When the antenna is submerged, the flap 32is closed by the hydrodynamic pressure of the water therearound inducedby the motion of the submarine to the position shown in full lines inFig. 2 and forms a fairing completing the streamline construction of theouter surface of the antenna in order to reduce to a minimum the dragpro duced by the antenna in passing through the water.

Throughout the specification I have used the terms front and rear withrespect to the electrical properties of the antenna. It will beappreciated that when traveling through the water the antenna is trailedwith its rear portion as considered above toward the front of thevessel. The same designations of front and rear with respect to theantenna are used in the appended claims.

From the foregoing description, it may be seen that I have provided anantenna adapted for use on submarines, which antenna has a streamlinedexterior configuration in order to reduce the drag of the antenna to aminimum, .wherein a parabolic reflector is used to focus the transverseelectromagnetic wave energy, and wherein the vertically polarized waveis rotated to a horizontal polarization by the novel use of a pluralityof steptwisted sections and then emanated from a sectoral horn array. Itis further evident that I have provided an antenna which provides abroadband impedance match to either air or water, whereby, if theantenna should be inadvertently submerged while the antenna is stillenergized, there will be no damage to the transmitter.

While I have shown and described the preferred form ofmy invention, itis to be understood that various modifications may be made thereinwithout departing from the spirit of the invention as defined in theappended claims.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. In a microwave system, a rectangular waveguide having a relativelylong side and a relatively short side, means for introducing microwaveenergy into said waveguide, a plurality of polarization rotatingelements each connected to said Waveguide adjacent each other in theplane of the relatively large dimension of said wave guide, each of saidpolarization rotating elements being adapted to receive a portion of thewave traveling through said waveguide and rotating the polarization ofsaid portion through 90, a plurality of adjacent radiating meansconnected one to each of said polarization rotating elements forradiating the said portions, whereby said portions will re-merge into asingle wave having its plane of polarization normal to the plane ofpolarization of the initial wave.

2. In a microwave system, a rectangular waveguide having a relativelylong side and a relatively short side, means for introducing planepolarized microwave energy into said waveguide, a plurality ofpolarization rotating elements each connected to said waveguide adjacenteach other in the plane of the relatively large dimension of saidwaveguide, each of said polarization rotating elements being adapted toreceive a portion of the polarized microwave energy traveling throughsaid waveguide and rotating the polarization of said portion through 90,a plurality of adjacent radiating means connected one to each of saidpolarization rotating elements for radiating the said portions, wherebysaid portions will re-merge into a single Wave having its plane ofpolarization normal to the plane of polarization of the initial wave.

3. In a microwave system, a parallel plate waveguide, means forintroducing microwave energy into said parallel plate waveguide, aplurality of polarizati n r t ting elements each connected to saidwaveguide adjacent each other in a plane parallel to the plane of midparallel plate waveguide, each of said polarization rotating elementsbeing adapted to receive a portion of the microwave energy travelingthrough said parallel plate waveguide and rotating the polarization ofsaid portion through a plurality of adjacent radiating means connectedone to each of said polarization rotating elements for radiating thesaid portions, whereby said portions will re-merge into a single wavehaving its plane of polarization normal to the plane of polarization ofthe initial wave.

4. In a microwave system, a parallel plate waveguide, means forintroducing plane polarized microwave energy into said parallel platewaveguide, a plurality of polarization rotating elements each connectedto said parallel plate waveguide adjacent each other in a plane parallelto the plane of said parallel plate waveguide, each of said polarizationrotating elements being adapted to receive a portion of the polarizedmicrowave energy traveling through said parallel plate waveguide androtating the polarization of said portion through 90", a plurality ofadjacent radiating means connected one to each of said polarizationrotating elements for radiating the said portions, whereby said portionswill remerge into a single wave having its plane of polarization normalto the plane of polarization of the initial wave.

5. In a microwave system, a rectangular waveguide having a relativelylong side and a relatively short side, means for introducing a planepolarized TEM wave into said waveguide, a plurality of polarizationrotating elements each connected to said waveguide adjacent each otherin the plane of the relatively large dimension vof said waveguide, eachof said polarization rotating elements being adapted to receive aportion of the wave traveling through said waveguide and rotating thepolarization of said portion through 90, a plurality of adjacentradiating means connected one to each of said polarization rotatingelements for radiating the said wave portions, whereby said waveportions will re-merge into a single wave having its plane ofpolarization normal to the plane of polarization of the initial wave.

6. In a microwave system, a parallel plate waveguide, means forintroducing a plane polarized T EM wave into said parallel platewaveguide, a plurality of polarization rotating elements each connectedto said parallel plate waveguide adjacent each other in a plane parallelto the plane of said parallel plate waveguide, each of said polarizationrotating elements being adapted to re ceive a portion of the wavetraveling through said parallel plate waveguide and rotating thepolarization of said portion through 90', a plurality of adjacentradiating means connected one to each of said polarization rotatingelements for radiating the said wave portions, whereby said waveportions will re-merge into a single wave having its plane ofpolarization normal to the plane of polarization of the initial wave. 7

7. In a microwave antenna, a parallelplate waveguide construction, aninput waveguide connected to said parallel plate waveguide for feedingmicrowaves into said parallel plate waveguide, an array of adjacentsectoral horns, and a plurality of step-twisted sections connecting theoutput end of said parallel plate waveguide with said array of sectoralhorns.

8. In a microwave antenna, a parallel plate waveguide construction, aninput waveguide connected to said parallel plate waveguide for feedingmicrowaves into said parallel plate waveguide, an array of adjacentsectoral horns, and a plurality of step-twisted sections connecting theoutput end of said parallel plate waveguide with said array of sectoralhorns, said sectoral horns being spaced a center to center distanceequal to at least one-half wavelength.

9. In a microwave antenna, a housing, a double-layer parallel platewaveguide construction in the lower portion of said housing, an inputwaveguide fixed to the rear of said housing for feeding TEM 'waves intosaid parallel plate waveguide, an array of horizontally adjacentsectoral horns in the upper portion of said housing, and a plurality ofhorizontally adjacent step-twisted sections connecting the output end ofsaid parallel plate waveguide with said array of sectoral horns.

10. In a submarine radar antenna, a housing, a doublelayer parallelplate waveguide construction in the lower portion of said housing, aninput waveguide fixed to the rear of said housing for feeding TEM wavesinto said parallel plate waveguide, an array of horizontally adjacentsectoral horns in the upper portion of said housing, a plurality ofhorizontally adjacent step-twisted sections connecting the output end ofsaid parallel plate waveguide with said array of sectoral horns, and adielectric window mounted in the flared end of each of said horns andsealed thereto, said windows being suitably shaped to provide abroadband impedance match to either air or water.

11. In a submarine radar antenna, a housing, a doublelayer parallelplate waveguide construction in the lower portion of said housing, aninput waveguide fixed to the rear of said housing for feeding TEM wavesinto said parallel plate waveguide, an array of horizontally adjacentsectoral horns in the upper portion of said housing, a plurality ofhorizontally adjacent step-twisted sections connecting the output end ofsaid parallel plate waveguide with said array of sectoral horns, certainof said horns being spaced an odd multiple of one-quarter wavelengthsbehind the remainder of said horns, and a dielectric window mounted inthe flared end of each of said horns and sealed thereto, said windowsbeing suitably shaped to provide a broadband impedance match to eitherair or water. 7

12. In a submarine radar antenna, a housing, a doublelayer parallelplate waveguide construction in the lower portion of said housing, aninput waveguide fixed to the rear of said housing for feeding TEM wavesinto said parallel plate waveguide, an array of horizontally adjacentsectoral horns in the upper portion of said housing, a plurality ofhorizontally adjacent step-twisted sections connecting the output end ofsaid parallel plate waveguide with said array of sectoral horns, saidsectoral horn array comprising an even number of horns whereinapproximately one-half of the horns are spaced an odd multiple ofone-quarter wavelengths behind the remainder of the horns and whereinthe horns are arranged symmetrically on either side of the axis ofpropagation of the system, a dielectric window mounted in the flared endof each of said horns and sealed thereto, said windows being suitablyshaped to provide a broadband impedance match to either air or water.

13. In a submarine radar antenna, a housing, a doublelayer parallelplate waveguide construction in the lower portion of said housing, aninput waveguide fixed to the rear of said housing for feeding TEM wavesinto said parallel plate waveguide, an array of horizontally adjacentsectoral horns in the upper portion of said housing, a plurality ofhorizontally adjacent step-twisted sections connecting the output end ofsaid parallel plate waveguide with said array of sectoral horns, saidsectoral horn array comprising an even number of horns and whereinapproximately one-half of the horns are spaced an odd multiple ofone-quarter wavelengths behind the remainder of the horns and whereinthe horns are arranged symmetrically on either side of the axis ofpropagation of the system, a dielectric window mounted in the flared endof each of said horns and sealed thereto, said windows being suitablyshaped to provide a broadband impedance match to either air or water,and a nonreflecting lossy dielectric adjacent the rear wall of saidhousing to absorb the back radiation of the Waveguide feed.

14. In a submarine radar antenna, a streamlined housing, the front halfof the top of said housing being hinged to the remainder of said housingand adapted to open to form one side of a flared horn, a double-layerparallel plate waveguide construction in the lower portion of saidhousing, an input waveguide fixed to the rear of said housing forfeeding TEM waves into said parallel plate waveguide, an array ofhorizontally adjacent sectoral horns in the upper portion of saidhousing, a plurality of horizontally adjacent step-twisted sectionsconnecting the output end of said parallel plate waveguide with saidarray of sectoral horns.

15. In a submarine radar antenna, a streamlined housing, the front halfof the top of said housing being hinged to the remainder of said housingand adapted to open to form one side of a flared horn, a double-layerparallel plate waveguide construction in the lower portion of saidhousing, an input waveguide fixed to the rear of said housing forfeeding TEM waves into said parallel plate waveguide, an array ofhorizontally adjacent sectoral horns in the upper portion of saidhousing, a plurality of horizontally adjacent step-twisted sectionsconnecting the output end of said parallel plate waveguide with saidarray of sectoral horns, a dielectric window mounted in the flared endof each of said horns and sealed thereto, said windows being suitablyshaped to provide a broadband impedance match to either air or water.

16. In a submarine radar antenna, a streamilend housing, the front halfof the top of said housing being hinged to the remainder of said housingand adapted to open to form one side of a flared horn, a double-layerparallel plate waveguide construction in the lower portion of saidhousing, an input waveguid fixed to the rear of said housing for feedingTEM waves into said parallel platewaveguide, an array of horizontallyadjacent sectoral horns in the upper portion of said housing, aplurality of horizontally adjacent step-twisted sections connecting theoutput end of said parallel plate waveguide with said array of sectoralhorns, certain of said horns being spaced one-quarter wavelength behindthe remainder of said horns, a dielectric window mounted in the flaredend of each of said horns and sealed thereto, said windows beingsuitably shaped to provide a broadband impedance match to either air orwater.

17. In a submarine radar antenna, a streamlined housing, the front halfof the top of said housing being hinged to the remainder of said housingand adapted to open to form one side of a flared horn, a double-layerparallel plate waveguide construction in the lower portion of saidhousing, an input waveguide fixed to the rear of said housing forfeeding TEM waves into said parallel plate waveguide, an array ofhorizontally adjacent sectoral horns in the upper portion of saidhousing, a plurality of horizontally adjacent step-twisted sectionsconnecting the output end of said parallel plate waveguide with saidarray of sectoral horns, said sectoral horn array comprising twenty-twohorns and wherein horns numbers 3, 4, 5, 9, 11, 13, 15, 16, 17, 21 and22 respectively are spaced one-quarter wavelength behind the remainderof the horns, a dielectric window mounted in the flared end of each ofsaid horns and sealed thereto, said windows being suitably shaped toprovide a broadband impedance match to either air or water.

18. In a submarine radar antenna, a streamlined housing, the front halfof the top of said housing being hinged to the remainder of said housingand adapted to open to form one side of a flared horn, a double-layerparallel plate waveguide construction in the lower portion of saidhousing, an input waveguide fixed to the rear of said housing forfeeding TEM waves into said parallel plate Waveguide, an array ofhorizontally adjacent sectoral horns in the upper portion of saidhousing, a plurality of horizontally adjacent step-twisted sectionsconnecting the output end of said parallel plate waveguide with saidarray of sectoral horns, said sectoral horn array comprising twenty-twohorns and wherein horns numbered 3, 4, 5, 9, 11, 13, 15, 16, 17, 21 and22 respectively are spaced one-quarter wavelength behind the remainderof the horns, a dielectric window mounted in the flared end of each ofsaid horns and sealed thereto, said windows being suitably shaped toprovide a broadband impedance match to either air or Water, and anon-reflecting lossy 5 dielectric adjacent the rear wall of said housingto absorb the back radiation of the wave guide feed.

References Cited in the file of this patent UNITED STATES PATENTS KingMay 26, 19 42 Purcell et a1 Aug. 19, 1952 Chu et a1 May 12, 1953 CohnFeb. 2, 1954

